What is Terra Firma?

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The Terra Firma Concept: Jitter is Analogue

July 2011, Part Two added Below

Preamble to the article: A number of people have commented and expressed some cynicism about the nature and content of the article below. "Nothing new" and  "advertising" and even that I didn't write the article, that it was written by Allen Wright. Not true, indeed he did not read it until after it was posted here. It has also been claimed that the article lack proper substance and explanation, which I dispute entirely.

Now it can be stated that the type of jitter discussed below has been measured/confirmed by Paul Miller in the UK, with access to equipment with 100 times the normal sensitivity and this magnification aimed at knowing where to look. Normal jitter does not cause digital sound (more like coluration we hear and adjust to in speakers). But this is a specific ultra-low level type of jitter not yet fully recognised for what it is and what it does.

This kind of jitter causes what we hear as digital sound, where tonal colours are bleached out and also the cause of longer term listener fatigue.

This type of jitter has been ignored as it looks like it is less than 1% of the total jitter spec and hence largely masked (but not by your ears). As the article states below, it is where in the audio spectrum where jitter shows up that is paramount. It is only a matter of time before the facts will become better known to others, our competitors. Until then we have the jump, below there are more than just hints at what is happening. Please go ahead and read with care and an open mind. Thank you. Joe Rasmussen.

The Terra Firma Concept: Jitter is Analogue

While we exist in a Digital Age, the environment that surrounds us, the physical world, is all analogue. When digital data (the content) has to be processed, it comes into an analogue world. The digital content is now a stream and is at the mercy of an analogue world. The content is maintained, but below the content the analogue world will put its own footprint.

And it is far more audible than we ever imagined!

Ultimate Digital Playback deserves Ultimate Stability!

On this Page:


The following are edited excerpts from an article written for the Audiophile Society of NSW, July 2008 Newsletter:

"Terra Firma" and Why Jitter Is Analogue?

I am excited and I have good reason to be. There is also reason for you to be excited as well. There have been some truly significants events that may well redefine digital playback once and for all time.

Some of you may have read March 2008 issue of The Absolute Sound a ground breaking review of the Esoteric G-0Rb "Atomic Clock. If you can get a copy of that issue, it is on Page 124 and very well worth the read. It may well be the most single significant article written in that magazine re digital audio.

This review by Robert Harley is already causing a stir in certain quarters and while the review subject is the Esoteric “Atomic Clock” is USD $15,000 there will not be a great market unless a mass produced low cost version is made and even then it will only be cheaper but NOT cheap. Even so, most mainstream players have no way of getting sync.

“The Esoteric G-0Rb Master Clock Generator rendered a much bigger gain in musical realism that I would have thought possible… It had a liquidity, ease, and naturalness that I’ve never heard before from digital audio reproduction. The hardness in the midrange, the glassy shattering sound on leading-edge transients, and the dynamic constriction were all gone, replaced by a silky smooth yet powerful rendering… more vivid… involving… sounding more like the real thing and less like synthetic recreations.”

He goes on at length that this is beyond any previous expectation he had of what he thought was the limits of CD playback.

But is this final great leap going to be beyond us Average Joes?

How Long Will It Take To Save $15.000?

But unconsciously Harley is pointing to another solution. While the sonic improvement is beyond question (I know because I and now others recognise they have heard the Holy Grail of digital clocking) he states that this Rubidium clock is power supply insensitive:

"Most other digital audio employ a voltage controlled crystal oscillator[VCXO]... Because the VCXO’s output frequency is a function of the voltage across it, any ripple or variations in the power supply will cause the frequency to change - the very definition of jitter... A Rubidium clock is not only more precise and stable than a VCXO; it is not subject to such variability in its output frequency."

(BTW, not all oscillators are really VCXOs, but Harley seems to use it as a generic description for powered oscillators rather than cheap crystal oscillators.)

Ahah! So the Rubidium clock is insensitive to power supply and oscillators are highlysensitive. If your player has a decent clock, it will be a powered oscillator. But does that mean that our oscillators  should all be thrown into the trash can? Far from doing that,realise the Achilles Heel may not the oscillator itself but the power supply that it is connected to. And this is something we are specialists in. So is there another way to get ‘Atomic’ quality clocking?

If we can stabilise the VCXO's power supply, extreme stability, then the performance of our more common garden oscillator (relative to Atomic Clocks) will take on a level of performance that will simply take your breath away.

How to Get Extreme Stability?

Harley talks about stability, he gets the point. This is surely the antidote to jitter. Our clock power supply needs to be as stable as the very ground we walk on; hence may I introduce you to the concept of Terra Firma. The earth is the biggest rock mass we can access and hence it has the greatest physical stability available. In the physical world, anything that moves will generally move in cycles. The equivalent electrical concept isAC. The earth, relative to our position in the physical world is DC. Now that is stability and this is our ultimate aim.

Some who work in various labs are familiar with heavy duty anti-vibration tables that are spiked to the ground - so tests can be performed that are not influenced by vibrations.

Is this perfect? No, but the aim is to be as stable as the very ground it sits on, DC like and expulse AC like movement. In above case the table sits on a steel enforced concrete slab set into compacted rock hard soil soil (often clay). The actual platform I have seen is a synthetic and extraordinary dense granite. In some cases there will be an anti-tuning device fitted under the platform or part of the frame. This is suitable for high powered microscopes. A commercial version designed for microscopes may look like this:

Can we make a power supply so rock like stable that it has the stability of our mother planet Terra Firma?

No, we cannot achieve it perfectly, but what we can produce is a power supply that hasextreme stability in a way that has not been done before. Just as the Atomic Clock is one way to achieve this extreme result, we now have a much more inexpensive solution that may well be proven even superior.

We can now look at CD and digital playback in an entire new light. I was among those back in 1983 that heard first generation players and it was quite horrible. There have been generational improvements along the way - not so much the technology persé but also the implementation of it. I say this because the now obsolete Philips TDA1541A came out in the second half of the 80's and to many still the most brilliant DAC ever. So why did they not sound that good back then (in fact they still sounded better than much of the pack). A modern implementation of a 1541A DAC is capable of superb analogue like sounds even today. Clock it right, get the fundamentals right too and it is pure magic. Only now are we getting a handle on what jitter really does. We hear it when it is banished.

Back to Harley: In his sidebar article on the History of Jitter he points out the disbelief by much of the Audio Engineering Society that bits were not just bits. The notion of jitter was considered lunacy - you had the credibility of necrophiles and paedophiles (I kid you not) and if you believed in it you were plainly a dangerous person.

"Put an analog signal down a wire, it degrades... not to mention subjecting the signal to every other component in the signal path... audiophiles noticed musically different variations between coaxial and Toslink connections, brands of digital cables - how could the sound change? What mysterious "X" factor that caused [proven] identical digital bitstreams to exhibit an analog-like variability."

That last phrase "analog-like variability" is indeed highly significant. Making physical changes to, not just cables, but other things that deal with the digital datastream - without loosing data - had an "analog-like variability" when converted to analogue and clearly audible. Hence it seemed that digital changes made for analogue like changes. Digital was not supposed to behave this way – bits were supposed to be bits, no matter what.

 You see: Jitter is Analogue!!!

Surely that cannot be? We think of jitter as a digital artefact, but quite plainly it is not (quantisation error is, but that is another subject). But it is oh so easy to prove. Back in the early days of CDs we noted that the laser pickup's output was a waveform, an analogue waveform (sorry, but I insist on spelling analogue correctly). In fact, you can display it on an analogue oscilloscope - there it is, right on a screen, a waveform.

Harley has previously pointed out that if your datastreams are identical, that is "zero for zero" and "one for one" throughout the stream, the classic binary code, then you have 100% data retrieval. If then these datastreams are converted and clearly sound different, it isn't some error correction but something below the level of that datastream. He then correctly made the conclusion, it can only be jitter.

 Jitter is “Sub Data Error”

Digital is the content, but analogue is the carrier or the form, the actual structure that propels the data. While digital exist as content alone, on your disk or music server hard drive, there is no jitter as such. But once it in motion it consists of a waveform, voltage, current, noise floor and full spectral content, it is all analogue in behaviour.

It is remarkable that we can now conclude that the error inherent in digital is all analogue, the content (program) is digital, the error content (jitter) is analogue.

While we exist in a Digital Age, the environment that surrounds us, the physical world, is all analogue. When digital data (the content) has to be processed, it comes into an analogue world. The digital content is now a stream and is at the mercy of an analogue world. The content is maintained, but below the content the analogue world will put its own footprint. And it is far more audible than we ever imagined.

In fact we are only really now, 25 years after the emergence of CD playback, become aware just how much jitter matters, as Harley concurs in his article.

For many years I have been witnessed by countless number of persons, saying that Low Frequency Jitter is the worst and most audible of all. I have stated ad nauseum  that power supply noise is the source of this worst kind of jitter and the noise floor should remain ultra-low down even to well under Sub One Hertz. Unfortunately, linear cum analogue circuits have by nature rising noise below 100 Hertz, just look at any published graph of any opamp and amplifier or power supply, there is a rise in both voltage and current noise, even the single humble transistor does this.

This is typical of all analogue circuits, in this case the highly acclaimed low noiseLM4562 now used by DEQX, Hypex and others. In fact, the above is above average (nominally 2.7nV/Hz) but rising well below 100Hz and still rising at and below 1 Hertz.

Edit 22/1/2013: There is an effect known as "Allan Variance" that may have a significant influence. This is a controversial subject as sub 1 Hertz deviations are not accepted as negatively infuincing at audio frequencies. Yet the Terra Firma Clock does indeed confirm sub 1 Hertz effects as critical to high-end digital audio.

As for batteries, they too are entirely inadequate. We have known that analogue noise is the enemy of all digital circuits since about 2003. Now we are learning exactly to what extent.

Again, can we see the connection? We have a VCXO that is usually powered by 3.3V - it needs power. The power we put into it has a noise content that can be defined spectrally.

The added jitter that comes out of the oscillator is directly proportional to the spectral content of the noise, analogue noise, not the digital content.

Hence, if we have Low Frequency noise (the worst kind), and the result is, the VCXO will add Low Frequency jitter. Higher frequency noise will add jitter content commensurate with that frequency. The analogue's spectral noise content is producing jitter of similar kind and frequency. It is as plain as that, analogue noise in, analogue jitter out. Jitter even has a frequency response! Again: Jitter is all analogue!

Harley is correct, the Esoteric Rubidium clock shows just how far we have fallen short, but this will not be the case much longer. The Atomic Clock’s superiority is as much due to the fact that the power supply dilemma demonstrated here is taken out of the equation. Now we come to the really good news. The Phoenix will rise from the ashes (trash can?), the VCXO will still emerge as everyman’s winner.

Do You Need a Bottomless Pocket?

No, and emphatically so. I believe these are exciting time, while some say that CDs are in a decline, the fact remains that digital playback is here to stay even if it will be music servers (hard drive) based and not optical playback, and we may see the demise of the CD player. But even Music Servers will need to be clocked once the content is read into a live stream.

The best news of all is simply this. We do not need to spend $15K and that affordable playback, that will scale new heights that few have yet even to imagine, is here.


Part Two (added July 2011)



Please also note the Blue box as we shall magnify it 100x later

Please note there are TWO measurements in the above graph, one is Black and over-layed on another Red measurement. Later we shall see the differences as we will look at and magnify 100x what is in the Blue square.

Some may have wondered why Terra Firma Clocks don't come with jitter specs? The reason is that Terra Firma takes an entirely different approach to jitter and also sorting out which KIND of jitter that is the most harnful as measured by the most powerful spectrum analyser we have, the ear.

We shall call it... UNL Jitter

In the above graph which is DUAL measurement of two different but related digital interfaces, one noted to sound quite superior to the other, but at the magnification shown above seems to hardly measure any different.

Yet the SOUND different!

Let me start with in analogy, two pairs of loudspeakers. For our purposes they are both of the same quality, have the same frequency response, both the same LF extension, low distortion through-out etc. So these speakers should sound very similar, but alas we are not surprised that they don't. They will still have a different "voice" and as such they can still be perceived as sounding different. Again, let us say state that they are both speakers of extreme high quality, their differences now really becomes a matter of taste and in selecting a preference, nothing more.

Now you may wonder what this has to do with jitter? It simply illustrates that jitter specs can be similar and yet the players sound different. Just like speakers, jitter can "voice" a player.

But the one thing we could never stomach in a speaker is DISTORTION, even if the frequency response is flat etc. If something is OBVIOUS, then there is a CAUSE.

Same goes with digital playback, we can become obsessed with jitter specs when in fact they only "voice" the playback sound. But in the above DUAL measurement graph, both very similar to the other, why did one sound so much better that the other.Something OBVIOUS must be happening. But this OBVIOUS thing is not apparent in the above measurement, so where now?

Could it be the is another jitter mechanism that is FAR WORSE?

Well, isn't jitter just jitter?

NO WAY! Indeed jitter can be MASKED by the actual jitter measurement itself.

The idea behind Terra Firma, from the moment the name was thought up, was that there are roughly two kinds of jitter. One that "voices" and the other that makes digital playback much less listenable than that good ol' analogue playback. And that form of jitter is generally masked and very difficult to measure. And yet it is OBVIOUS.

Terra Firma targets jitter that is caused by "Low Rate Uncorrelated or Noise-Like Jitter" - to quote Paul Miller.

So there you are, we even have a "name" for it, albeit a cumbersome one.

This kind of jitter is very hard to measure. But it is also the kind of jitter that makes digital sound DIGITAL. Peculiarly, the other forms of jitter are far more likely to make sonic differences that are perceived as analogue differences. Hence we can hear the differences in digital cables etc., as Harley points out, things like digital cables takes on analogue behaviour.

But rarely are these difference DESTRUCTIVE in nature, more like "voicing" in speakers and we pick our preferences.

But we are targeting something beyond "voicing" - something OBVIOUS to the ear as WRONG, something we have collectively coined... DIGITITUS !!!

UNL Jitter, Uncorrelated Noise-Like Jitter.

Let us look at an actual example:

Please also note the Blue box above magnified by a factor 100x

(Is this a measurement revealing "Allan Variance"?)

In the DUAL graph in the first graph, we can see that there was very little difference between Red and Black, but it was also stated that Black was observed to sound quite a bit better than Red.

Now what was contained in the Blue box has been magnified something like 100x - and NOW we can see a significant different. UNL Jitter is very obvious. This was a measurement made by some extreme piece of measurement worth hundreds of thousand dollars (by Paul Miller). I doubt any clock manufacturer have access to something capable of this, we certainly do not.

But do not despair, the effect is quite audible and a product that tackles UNL Jitter can be done simply by knowing what you are targeting and the LISTEN to it.

A few comments re above magnified DUAL graph: 

From the previous first graph above we can see that the sidebands are clearly within normal audio bandwidth, we can also see their relative amplitude.

Now closely examine what happen with the Red overlayed under Black. We can see Red clinging and rising with the fundamental and I can see some thing up to near -70dB - and now compare that none of the sidebands are worse than -120dB, and this is truly DISTURBING. Even at 40dB difference in amplitude, were are talking about 100x the amplitude, and possibly much worse than that at it is masked on potentially several fronts and likely to be much worse than that. In regular jitter measurements, UNL Jitterwon't even show up, and is probably less than 1% of the overall jitter measurement. Yet it is catastrophic in behaviour. If in doubt, look at the AMPLITUDE of UNL Jitter.

In above example I see at least 50dB (300x), but I suspect even higher levels of magnification will reveal much higher AMPLITUDE. The problem is that the fundamental is doing its level best to mask it.

It is also clear that we are talking about ULTRA-ULTRA-LOW FREQUENCY behaviour. How low, you may ask? Initially we targeted low hundreds of a Hertz, then in the thousandths of a Hertz, finally millionths of a Hertz. And it was very audible, even in blind tests.

Is this something that is not fully understood? Both Allen and I agreed that was the case. I made the point how can something that takes so long to eventuate yet still show up within the audio band, simply because the time constant is so long, how can it show up in music that is a series of short term events. 

Maybe think something quantum going on? It is an intriguing thought.

What is clear is this to measure UNL Jitter is for real, because it can be seen by exceptional measurement systems, but yet difficult to put a quantifiable number on it.

Joe Rasmussen

At the Cross Roads


(Above article is an edited version of article published in the July 2008 issue of ASoN's Newsletter.)



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Just had a terrible thought. If "intelligent design" is unscientific, then who will design our audio equipment?